Photoconductive elements containing substituted triarylamine photoconductors

ABSTRACT

TRIARYLAMINES HAVING AT LEAST ONE OF THE ARYL RADICALS SUBSTITUTED BY EITHER A VINYL RADICAL OR A VINYLENE RADICAL HAVING AT LEAST ONE ACTIVE HYDROGEN-CONTAINING GROUP ARE GOOD ORGANIC PHOTOCONDUCTORS IN ELECTROPHOTOGRAPHIC SYSTEMS.

United States Patent 3,567,450 PHOTOCONDUCTIVE ELEMENTS CON- TAININGSUBSTITUTED TRllARYL- AMINE PHOTOCONDUCTORS Thomas B. Brantly, LawrenceE. Contois, and Charles J. Fox, Rochester, N.Y., assignors to EastmanKodak Company, Rochester, N.Y. No Drawing. Filed Feb. 20, 1968, Ser. No.706,800 Int. Cl. 603g 5/06, 13/22 US. Cl. 96--1.5 17 Claims ABSTRACT OFTHE DISCLOSURE Triarylamines having at least one of the aryl radicalssubstituted by either a vinyl radical or a vinylene radical having atleast one active hydrogen-containing group are good organicphotoconductors in electrophotographic systems.

This invention relates to electrophotography, and in particular tophotoconductive compositions and elements.

The process of xerography, as disclosed by Carlson in US. 2,297,691,employs an electrophotographic element comprising a support materialbearing a coating of a normally insulating material whose electricalresistance Varies with the amount of incident actinic radiation itreceives during an imagewise exposure. The element, commonly termed aphotoconductive element, is first given a uniform surface charge,generally in the dark after a suitable period of dark adaptation. It isthen exposed to a pattern of actinic radiation which has the effect ofdifferentially reducing the potential of the surface charge inaccordance with the relative energy contained in various parts of theradiation pattern. The differential surface charge or electrostaticlatent image remaining on the electrophotographic element is then madevisible by contacting the surface with a suitable electroscopic markingmaterial. Such marking material or toner, whether contained in aninsulating liquid or on a dry carrier, can be deposited on the exposedsurface in accordance with either the charge pattern or the dischargepattern as desired. The deposited marking material can then be eitherpermanently fixed to the surface of the sensitve element by known meanssuch as heat, pressure, solvent vapor, or the like, or transferred to asecond element to which it can similarly be fixed. Likewise, theelectrostatic latent image can be transferred to a second element anddeveloped there.

Various photoconductive insulating materials have been employed in themanufacture of electrophotographic elements. For example, vapors ofselenium and vapors of selenium alloys deposited on a suitable supportand particles of photoconductive zinc oxide held in a resinous,film-forming binder have found wide application in present-day documentcopying applications.

Since the introduction of electrophotography, a great many organiccompounds have also been screened for their photoconductive properties.As a result, a very large number of organic compounds are known topossess some degree of photoconductivity. Many organic compounds haverevealed a useful level of photoconduction and have been incorporatedinto photoconductive compositions. Optically clear organicphotoconductor-containing elements having desirable electrophotographicproperties can be especially useful in electrophotography. Suchelectrophotographic elements can be exposed through a transparent baseif desired, thereby providing unusual flexibility in equipment design.Such compositions, when coated as a film or layer on a suitable supportalso yield an element which is reusable; that is, it can be used to formsubsequent images after residual toner from prior images 3,567,450Patented Mar. 2, 1971 has been removed by transfer and/or cleaning. Thusfar, the selection of organic compounds for incorporation intophotoconductive compositions to form electrophotographic layers hasproceeded on a compound by compound basis. Nothing has yet beendiscovered from the large number of different photoconductive substancestested which permits effective prediction and therefore selection ofparticular compounds exhibiting the desired electrophotographicproperties.

It is, therefore, an object of this invention to provide photoconductiveelements for use in electrophotography containing a novel class oforganic photoconductors having enhanced photosensitivity whenelectrically charged.

It is also an object to provide electrophotographic elements having alayer of a novel photoconductive composition which can be positively ornegatively charged.

It is another object to provide novel transparent electro photographicelements having high speed characteristics.

It is a further object of this invention to provide novelelectrophotographic elements useful for producing imageselectrophotographically by reflex or birefiex processes.

These and other objects of this invention are accomplished withelectrophotographic elements having coated thereon organicphotoconductive compositions containing a triarylamine photoconductorwherein at least one of the aryl radicals is substituted by either avinyl radical or a vinylene radical having at least one activehydrogencontaining group. The phrase vinylene radical includessubstituted as well as unsubstituted vinylene radicals and also includesthose radicals having at least one and as many as three repeating unitsof vinylene groups such as tCH=CH+ wherein n is an integer of from oneto three. Groups which contain active hydrogen are well known in theart, the definition of this term being set forth in several textbookssuch as Advanced Organic Chemistry, R. C. Fuson, pp. 154157, John Wiley& Sons, 1950'. The term active hydrogen-containing group as used hereinincludes those compounds encompassed by the discussion in the textbookcited above and in addition includes those compounds which containgroups which are hydrolyzable to active hydrogen-containing groups.Typical active hydrogen-containing groups substituted on the vinyleneradical of the triarylamine according to this invention include:

(a) carboxy radicals,

(b) hydroxy radicals,

(c) ethynyl radicals including substituted ethynyl radicals such ashydroxy ethynyl radicals, aryl ethynyl radicals and alkyl ethynylradicals,

(d) ester radicals (e.g.,

0 ll -ooR wherein R is alkyl or aryl) including cyclic ester radicals 0ll -COR wherein R is a cyclic alkylene radical connected to a vinylenecombination such as is found in coumarin de rivatives, (e) carboxylicacid anhydride radicals, (f) semicarbazono radicals, (g) cyano radicals,(h) acyl halide radicals (e.g.,

etc.), and

(i) amido radicals (e.g.,

o R H -C-N wherein R is a hydrogen atom, an alkyl group or an arylgroup).

Other active hydrogen-containing groups include substituted andunsubstited al kylidyne oximido radicals.

The preferred photoconductors of this invention are represented by thefollowing structure:

Ar;- :0 X 1.4 (I. i.

wherein:

(a) Ar and Ar are each a phenyl radical including a substituted phenylradical such as a halophenyl radical, an al kyl phenyl radical or anaminophenyl radical;

(b) Ar is an arylene radical including a substituted arylene radicalsuch as a phenylene radical or a naphthylene radical,

(c) R and R are each hydrogen, a phenyl radical including a substitutedphenyl radical or a lower alkyl radical preferably having 1-8 carbonatoms;

(d) X is either (1) an active hydrogen-containing group such as acarboxy radical, an acyl halide radical, an amido radical, a carboxylicacid anhydride radical, an ester radical, a cyano radical, a hydroxyradical, a semicarbazone radical, an ethynyl radical, or a methylidyneoximido radical or (2) hydrogen, provided that when X is hydrogen R andR are also hydrogen; and

(e) n is an integer of one to three.

The vinyl or vinylene radical can be substituted in any position on thearylene nucleus. However, when Ar is phenylene, particularly goodresults are obtained if the substitution occurs in the para position.

The organic photoconductors of this invention exhibit substantialimprovements in speed over comparable photoconductors which do not haveboth an active hydrogencontaining group (including groups hydrolyzableto active hydrogen-containing groups) and a vinyl or vinylene group.Also, those compounds having an unsubstituted vinyl radical showimprovements in electrical speed as organic photoconductors whencompared to similar compounds which lack such a group. Thus, a compoundaccording to the above formula when n is zero and X is an activehydrogen-containing group would not exhibit the higher speeds attainablewhen compared to a compound where n is 1, 2, or 3. Furthermore, if X isa group other than an active hydrogen-containing group or hydrogen (andn is 1, 2 or 3), the photoconductivity of the resulting compound isgenerally lower than that attainable if such groups are present.Finally, if X is a group other than an active hydrogen-containing groupor hydrogen and n in the above formula is zero, the resultant speedsattainable from such compounds when used as organic photoconductors aresomewhat lower than those attainable from comparable compounds accordingto this invention.

Those compounds in which Ar; and Ar in the above formula are phenylradicals generally have improved photo-conducting properties over thosewhich are substituted by one or two alkyl or benzyl radicals. Thus,pdiphenyl amino-cinnamic acid and methyl p-diphenylaminocinnamatedisplay improved electrical speeds over p-(N-methyl,N-phenylamino)cinnamic acid, methyl p- (N-imethyl,N-phenylamino)cinnamate or methyl p-dibenzylaminocinnamate. Also, ethylp-diphenylaminophenylvinylacrylate has enhanced electrical speedproperties compared to ethyl p-dimethylaminophenylvinylacrylate.

Some typical photoconductors of this invention are:

Table I (I) 4- (p-diphenylaminophenyl) -3-buten1-yne (II)p-diphenylaminostyrene (III) ethyl p-diphenylaminocinnamate (IV) methylp-diphenylaminocinnamate (V) p-diphenylaminocinnamoyl chloride (VI)p-diphenylaminocinnamic acid N,N-diphenylamide (VII)p-diphenylaminocinnamic acid anhydride (VIII)3-(p-diphenylaminophenyl)-2-butenoic acid (IX) bis(p-diphenylaminobenzal)succinic acid (X)4-N,N-bis(p-bromophenyl)aminocinnaimic acid (XI)1-(4-diphenylamino)naphthacrylic acid (XII) p-diphenylaminocinnamic acid(XIII) p-diphenylaminocinnamonitrile (XIV) 7-diphenylamino coumarin (XV)p-diphenylaminophenylvinylacrylic acid (XVI) p-diphenylaminobenzylp-diphenylaminocin namate (XVII) 7- (p-diphenylaminostyryl) coumarin(XVIII) p-diphenylaminocinnamyl alcohol (XIX)4-diphenylaminocinnamaldehyde semicarbazone (XX)O-p-diphenylaminocinnamoyl p'-diphenylaminobenzaldehyde oxime (XXI)p-diphenylaminocinnamaldehyde oxime, and

(XXII) 1,3-bis (p-diphenylaminophenyl)-2-propen-1-ol These compounds canbe prepared by the methods set forth in a copending application filedconcurrently herewith entitled Novel Substituted Triarylamines, SerialNumber 706,799, filed Feb. 20, 1968.

:Electrophotographic elements of the invention can be prepared withthese photoconducting compounds in the usual manner, i.e., by blending adispersion or solution of a photoconductive compound together with abinder, when necessary or desirable, and coating or forming aself-supporting layer with the photoconductor-containing materials.Mixtures of the photoconductors described herein can be employed.Likewise, other photoconductors known in the art can be combined withthe present photoconductors. In addition, supplemental materials usefulfor changing the spectral sensitivity or electrophotosensitivity of theelement can be added to the composition of the element when it isdesirable to produce the characteristic effect of such materials.

Sensitizing compounds useful with the photoconductive compounds of thepresent invention can include a wide variety of substances such aspyrylium, thiapyrylium, and selenapyrylium salts of US. Patent3,250,615, issued May 10, 1966; fluorenes, such as7,12-dioxo-l3-dibenzo(a,h) fluorene, 5,10dioxo-4a,11-diazabenzo(b)fluorene, 3,13-dioxo-7-oxadibenzo-('b,g)fluorene, trinitrofluorenone,tetranitrofiuorenone and the like; aromatic nitro compounds of US.Patent 2,610,120; anthro-nes of US. Patent 2,670,- 285; quinones of US.Patent 2,670,286; benzophenones of US. Patent 2,670,287; thiazoles ofUS. Patent 2,732, 301; mineral acids; carboxylic acids, such as maleicacid, dichloroacetic acid, and salicylic acid; sulfonic and phosphoricacids; and various dyes such as triphenylmethane, diarylmethane,thiazine, azine, oxazine, Xanthene, phthalein, acridine, azo,anthraquinone dyes and many other suitable sensitizing dyes. Thepreferred sensitizers for use with the compounds of this invention arepyrylium and thiapyrylium salts, fluorenes, carboxylic acids, andtriphenylmethane dyes.

Where a sensitizing compound is to be used within a photoconductivelayer as disclosed herein it is conventional practice to mix a suitableamount of the sensitizing compounds with the coating composition sothat, after thorough mixing, the sensitizing compound is uniformlydistributed throughout the desired layer of the coated element. Inpreparing the photoconducting layers, no sensitizing compound is neededfor the layer to exhibit photoconductivity. The lower limit ofsensitizer required in a particular photoconductive layer is, therefore,zero. However, since relatively minor amounts of sensitizing compoundgive substantial improvement in the electrophotographic speed of suchlayers, the use of some sensitizer is preferred. The amount ofsensitizer that can be added to a photoconductor-incorporating layer togive effective increases in speed can vary widely. The optimumconcentration in any given case will vary with the specificphotoconductor and sensitizing compound used. In general, substantialspeed gains can be obtained where an appropriate sensitizer is added ina concentration range from about 0.0001 to about percent by weight basedon the weight of the film-forming coating composition.

Generally, a sensitizer is added to the coating composi-' tion in anamount by weight from about 0.005 to about 5.0 percent by Weight of thetotal coating composition.

Preferred binders for use in preparing the present photoconductivelayers are film-forming polymeric binders having fairly high dielectricstrength which are good electrically insulating film-forming vehicles.Materials of this type comprise styrene-butadiene copolymers; siliconeresins; styrene-alkyd resins; silicone-alkyd resins; soya-alkyd resins;poly(vinyl chloride); poly(vinylidene chloride); vinylidenechloride-acrylonitrile copolymers; poly(vinyl acetate); vinylacetate-vinyl chloride copolymers; poly(vinyl acetals), such aspoly(vinyl butyral); polyacrylic and methacrylic esters, such aspoly(methylmethacrylate), poly(n-butylmethacrylate) poly (isobutylmethacrylate), etc.; polystyrene; nitrated polystyrene;polymethylstyrene; isobutylene polymers; polyesters, such aspoly(ethylenealkaryloxyalkylene terephthalate); phenol-formaldehyderesins; ketone resins; polyamides; polycarbo-nates; polythiocarbonates;poly(ethylene-glycol-cobishydroxyethoxy-phenyl propane terephthalate);nuclear substituted vinyl haloarylates such as poly(vinylmetabromobenzoate-co-vinyl acetate); etc. Methods of making resins ofthis type have been described in the prior art, for example,styrene-alkyd resins can be prepared according to the method describedin U.S. Patents 2,361,019 and 2,258,423. Suitable resins of the typecontemplated for use in the photoconductive layers of the invention aresold under such trade names as Vitel PE101, Cymac, Piccopale 100, SaranF220 and Lexan 105. Other types of binders which can be used in thephotoconductive layers of the invention include such materials asparaffin, mineral waxes, etc.

Solvents of choice for preparing coating compositions of the presentinvention can include a number of solvents such as benzene, toluene,acetone, Z-butanone, chlorinated hydrocarbons, e.g., methylene chloride,ethylene chloride, etc., ethers, e.g., tetrahydrofuran, or mixtures ofthese solvents etc.

In preparing the coating composition useful results are obtained wherethe photoconductor substance is present in an amount equal to at leastabout 1 weight percent of the coating composition. The upper limit inthe amount of photoconductor substance present can be widely varied inaccordance with usual practice. In those cases where a binder isemployed, it is normally required that the photoconductor substance bepresent in an amount from about 1 weight percent of the coatingcomposition to about 99 weight percent of the coating composition. Apreferred Weight range for the photoconductor substance in the coatingcomposition is from about 10 weight percent to about 60 weight percent.

Coating thicknesses of the photoconductive composition on a support canvary widely. Normally, a coating in the range of about 0.001 inch toabout 0.01 inch before drying is useful for the practice of thisinvention. The preferred range of coating thickness was found to be inthe range from about 0.002 inch to about 0.006 inch before dryingalthough useful results can be obtained outside of this range.

Suitable supporting materials for coating the photoconductive layers ofthe present invention can include any of a wide variety of electricallyconducting supports, for example, paper (at a relative humidity above 20percent); aluminum-paper laminates; metal foils such as aluminum foil,zinc foil, etc.; metal plates, such as aluminum, copper, zinc, brass,and galvanized plates; vapor deposited metal layers such as silver,nickel, or aluminum and the like. Metal (e.g., nickel, etc.) conductinglayers deposited by high vacuum deposition techniques can be coated atlow coverages so as to be substantially transparent to facilitate imageexposure through the support. An especially useful conducting supportcan be prepared by coating a support material such as poly(ethyleneterephthalate) with a layer containing a semiconductor dispersed in aresin. Suitable conducting layers both with and without insulatingbarrier layers are described in US. Patent 3,245,833. Other suitableconducting layers are described in U.S. Patent 3,120,- 028. Likewise, asuitable conducting coating can be prepared from the sodium salt of acarboxyester lactone of maleic anhydride and a vinyl acetate polymer.Such kinds of conducting layers and methods for their optimumpreparation and use are disclosed in US. 3,007,901 and 3,267,807.

The elements of the present invention can be employed in any of thewell-known electrophotographic processes which require photoconductivelayers. One such process is the aforementioned xerographic process. Aspreviously explained, in a process of this type the electrophotographicelement is given a blank electrostatic charge by placing the same undera corona discharge which serves to give a uniform charge to the surfaceof the photoconductive layer. This charge is retained by the layer owingto the substantial insulating property of the layer, i.e., the lowconductivity of the layer in the dark. The electrostatic charge formedon the surface of the photoconducting layer is then selectivelydissipated from the surface of the layer by exposure to light through animage-bearing transparency by a conventional exposure operation such as,for example, by contact-printing techniques, or by lens projection of animage, etc., to form a latent image in the photoconducting layer. Byexposure of the surface in this manner, a charge pattern is created byvirtue of the fact that light causes the charge to be conducted away inpro portion to the intensity of the illumination in a particular area.The charge pattern remaining after exposure is then developed, i.e.,rendered visible, by treatment with a medium comprisingelectrostatically attractable particles having optical density. Thedeveloping electrostatically attractable particles can be in the form ofa dust, e.g., powder, pigment in a resinous carrier, i.e., toner, or aliquid developer may be used in which the developing particles arecarried in an electrically insulating liquid carrier. Methods ofdevelopment of this type are widely known and have been described in thepatent literature in such patents, for example, as US. Patent 2,297,691and in Australian Patent 212,315. In processes of electrophotographicreproduction such as in xerography, by selecting a developing particlewhich has as one of its components, a low-melting resin, it is possibleto treat the developed photoconductive material with heat to cause thepowder to adhere permanently to the surface of the photoconductivelayer. In other cases, a transfer of the image formed on thephotoconductive layer can be made to a second support, which would thenbecome the final print. Techniques of the type indicated are well knownin the art and have been described in a number of US. and foreignpatents, such as US. Patents 2,297,691 and 2,551,582, and in RCA Review,vol. 15, (1954) pages 469484.

The present invention is not limited to any particular mode of use ofthe new electrophotographic materials, and the exposure technique, thecharging method, the transfer (if any), the developing method, and thefixing method as Well as the materials used in these methods can beselected and adapted to the requirements of any particular technique.

Electrophotographic materials according to the present invention can beapplied to reproduction techniques wherein different kinds ofradiations, i.e., electromagnetic radiations as well as nuclearradiations, can be used. For this reason, it is pointed out herein thatalthough materials according to the invention are mainly intended foruse in connection with methods comprising an exposure, the termelectrophotography wherever appearing in the description and the claims,is to be interpreted broadly and understood to comprise both xerographyand xeroradiography.

The following examples are included for a further understanding of theinvention.

EXAMPLE 1 Organic photoconductors of the type described herein areseparately incorporated into a coating dope having the followingcomposition:

Organic photoconductor: 0.5 g. Polymeric binder: 1.05 g. Sensitizer:0.02 g.

Methylene chloride: 11.7 mi.

The resulting compositions are coated at a wet thickness of 0.004 inchon a conducting layer comprising the sodium salt of a carboxyesterlactone, such as described in US 3,120,028, which in turn is coated on acellulose acetate film base. The coating blocks are maintained at atemperature of 90 F. These electrophotographic elements are chargedunder a positive or negative corona source until the surface potentials,as measured by an electrometer probe, reach between about 500 and 600volts. They are then subjected to exposure from behind a stepped densitygray scale to a 3000 K. tungsten source. The exposure causes reductionof the surface potentials of the elements under each step of the grayscale from their initial potential, V0, to some lower potential, V Whoseexact value depends on the actual amount of exposure inmeter-candleseconds received by the areas. The results of the measurements are plotted on a graph of surface potential V vs. log exposure foreach step. The speed is the numerical expression of 10 multiplied by thereciprocal of the exposure in meter-candle-seconds required to reducethe 500 to 600 volt charged surface potentials to 100 volts above volt.The reduction of the surface potential to 100* volts or below issignificant in that it represents a requirement for suitable broad areadevelopment of a latent image. This speed at 100 volts is a measure ofthe ability to produce and hence forth to develop or otherwise utilizethe latent image, higher speeds requiring less illumination to produce alatent image. When the photoconductor is absent from the coating, thesurface potential does not drop to, or below, 100 volts and no speedvalue can be assigned. This is also the case when a compound is presentin the composition but is ineffective as a photoconductcr. The speeds ofthe various photoconductive compositions are shown in Table 11 below.The sensitizers used are referred to below as follows:

(E) 2,6-'( 4-e-thylphenyl -4- (4-amyloxyphenyl thiapyrylium perchlorate(F) 2,4-bis 4-ethoxyphenyl) -6- (4-n-amyloxystyryl)pyrylium fluoborate(G) 2,4-bis 4-ethylphenyl -6- (4-styryistyryl) pyryliurn perchlorate (H).2,6-bis (4-ethoxyphenyl) -4- (4-n-amyloxy-phenyl) thiapyryliumperchlorate The data in the following Table II represents the positivespeeds at 100 volts of various compositions prepared as described abovecontaining severai of the organic photoconductors set forth in Table I.The binder employed is poly(vinyl meta-bromobenzoate-co-vinyl acetate).

TABLE II Speed at volts sensitizer Photoconduetor F G H The latentelectrostatic images in each instance developed with conventionalelectrophotographic liquid developers (e.g., U.S. Patent 2,907,674) toform sharp dense images.

EXAMPLE 2 Example 1 is repeated except that the binder employed is afilm-forming polycarbonate resin sold commercially as Lexan by GeneralElectric Co. The photoconductor employed in the photoconductivecomposition is p-diphenylaminocinnamoyl chloride (Compound V). Thepositive speed at 100 volts for compositions containing sensitizer F is260 and for sensitizer G the speed is 220.

EXAMPLE 3 In order to show the efiicacy of the vinylene moiety in thephotoconductors of this invention, two closely related compounds aretested for their electrophotographic speeds at 100 volts positive. Thefirst compound, p-diphenylaminocinnamic acid (Compound XII) has avinylene moiety While the second, 4-carboxytriphenylamine, is the sameas compound XII but lacks a vinylene moiety. Two photoconductivecompositions are prepared and tested according to Example 1 except thefollowing composition is used:

Photoconductor: 0.15 g. Binder Vitel 101 0.50 g. Sensitizer F: 0002 g.Dichlorornethane: 5.0 ml.

1 A polyester of te'rephthalie acid and a mixture of ethylene glycol (1part by weight) and 2, 2-bis[ l-(B-hyrlroxyethoxy) phenyl1propane (9parts by weight).

The speed of 4-carboxytriphenylamine is 50. The speed of Compound XII is160.

EXAMPLE 4 This example demonstrates the increases in speed attainablewith a photoconducting compound having both a vinylene moiety and anactive hydrogen-containing group such as compound XII as opposed to aphotoconducting compound having neither moiety present such astriphenylamine. Thus, photoconducting compositions containing the abovephoto-conductors are prepared and tested according to Example 1 exceptthe following composition is used:

Photoconductor: 1.0 g.

Binder, poly(vinyl meta-bromo-henzoate-co-vinyl acetate): 1.0 g.

Sensitizer G: 0.02 g.

Dichloromethane: 11.7 ml.

The positive 100 volt speed of the composition containing triphenylamineis 130. The positive 100 volt speed of the composition containingcompound XI-I is 630.

EXAMPLE 6 EXAMPLE 7 The 100 volt positive speed ofp-diphenplaminocinnamonitrile is determined according to Example 1 usingthe following composition:

Photoconductor: 0.15 g. Vitel 101: 0.50 g. Sensitizer G: 0.002 g.Dichloromethane: 5.0 ml.

The resultant speed is 110.

EXAMPLE 8 Coating dopes prepared in the manner set forth in Example 1containing the compounds in Table I are coated in the manner describedin Example 1. In a darkened room, the surface of each of thephotoconductive layers so prepared is charged to a potential of about+600 volts under a corona charger. The layer is then covered with atransparent sheet bearing a pattern of opaque and light transmittingareas and exposed to the radiation from an incandescent lamp with anillumination intensity of about 75 meter-candles for 12 seconds. Theresulting electrostatic latent image is developed in the usual manner bycascading over the surface of the layer a mixture of negatively chargedblack thermoplastic toner particles and glass beads. A good reproductionof the pattern results in each instance.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinbefore and as defined in the appendedclaims.

We claim:

1. An electrophotographic element comprising a conductive support havingcoated thereon a photoconductive composition comprising a photoconductorhaving the structure:

an ethynyl radical, an acyl halide radical, a cyano radical, acarboxylic acid anhydride radical, a hydroxy radical, a semicarbazonoradical, an oximido radical and an amido radical; and

(e) n is an integer of 1 to 3.

2. A photoconductive element as defined by claim 1 wherein thephotoconductive composition contains a sensitizer for saidphotoconductor.

3. An electrophotographic element as defined in claim 1 wherein thephotoconductive composition is sensitized with a compound selected fromthe group consisting of:

(a) a pyrylium salt,

(b) a thiapyrylium salt,

(0) a selenapyrylium salt,

(d) a fiuorenone, and

(e) a triphenylmethane dye.

4. An electrophotographic element as defined in claim 4 wherein a binderis utilized for the photoconductor, said binder being a polymer of anuclear substituted vinyl haloarylate.

5. An electrophotographic element as defined in claim 4 wherein apoly(ethylenealkaryloxykylene terephthalate) binder is utilized for thephotoconductor.

6. An electrophotographic element comprising an electrically conductivesupport having coated thereon a photoconductive composition comprising apolymeric binder and a photoconductor selected from the group consistingof: I

(a) ethyl p-diphenylaminocinnamate,

(b) methyl p-diphenplaminocinnamate,

(c) p-diphenylaminocinnamoyl chloride,

((1) p-diphenylaminocinnamic acid N,N diphenylamide,

(e) p-diphenylaminocinnamic acid,

(f) p-diphenylaminocinnamic acid anhydride,

(g) 3-(p-diphenylaminophenyl)-2-butenoic acid,

(h) 4-N,N-bis (p-bromophenyl)aminocinnamic acid,

(i) bis (p-diphenylaminobenzal)succinic acid,

(j) l-(4-diphenylamino)naphthacrylic acid,

(k) p-diphenylaminocinnamonitrile,

(l) p-diphenylaminostyr-ene,

(m) p-diphenylaminophenylvinylacrylic acid, and

(n) 7-diphenylamino coumarin.

7. A photoconductive element for use in electrophotography comprising aconductive support having coated thereon a photoconductive compositioncomprising:

(a) about 10 to 60% by weight based on said photoconductive compositionof methyl p-diphenylaminocinnamate as a photoconductor, and

(b) a film-forming polymeric binder for said photoconductor.

8. A photoconductive element for use in electrophotography comprising aconductive support having coated thereon a photoconductive compositioncomprising:

(a) about 10 to 60% by weight based on said photoconductive compositionof p-diphenylaminocinnamic acid anhydride as a photoconductor, and

(b) a film-forming polymeric binder for said photoconductor.

9. A photoconductive element for use in electrophotography comprising aconductive support having coated thereon a photoconductive compositioncomprising:

(a) about 10' to 60% by weight based on said photoconductive compositionof 3-(p-diphenylarninophenyl)-2-butenoic acid as a photoconductor, and

(b) a film-forming polymeric binder for said photoconductor.

10. A photoconductive element for use in electrophotography comprising aconductive support having coated thereon a photoconductive compositioncomprising:

(a) about 10 to 60% by weight based on said photoconductive compositionof p-diphenylaminocinnamic acid as a photoconductor, and

(b) a film-forming polymeric binder for said photoconductor.

11. A photoconductive element for use in electrophotography comprising aconductive support having coated thereon a photoconductive compositioncompris- (a) about 10 to 60% by weight based on said photoconductivecomposition of ethyl p-diphenylamino cinamate as a photoconductor, and

(b) a film-forming polymeric binder for said photoconductor.

12. A photoconductive element for use in electrophotography comprising aconductive support having coated thereon a photoconductive compositioncomprismg:

(a) about 10 to 60% by Weight based on said photoconductive compositionof methyl p-diphenylaminocinnamate as a photoconductor,

(b) about 0.005 to 5.0% by weight based on said photoconductivecomposition of a pyrylium salt as a sensitizer, and

(c) poly(vinyl meta-bromobenzoate-co-vinyl acetate) as a binder for saidphotoconductor.

13. A photoconductive element for use in electrophotography comprising aconductive support having coated thereon a photoconductive compositioncomprismg:

(a) about 10 to 60% by weight based on said photoconductive compositionof p-diphenylarninocinnamic acid anhydride as a photoconductor,

(b) about 0.005 to 5.0% by weight based on said photoconductivecomposition of a pyrylium salt as a sensitizer, and

(c) poly(viny1 metabromobenzoate-co-vinyl acetate) as a binder for saidphotoconductor.

14. A photoconductive element for use in electrophotography comprising aconductive support having coated thereon a photoconductive compositioncomprismg:

(a) about 10 to 60% by weight based on said photoconductive compositionof 3-(p-diphenylaminopheny1)-2-butenoic acid as a photoconductor,

(b) about 0.005 to 5.0% by weight based on said photoconductivecomposition of a pyrylium salt as a sensitizer, and

(c) poly(vinyl meta-bromobenzoate-co-vinyl acetate) as a binder for saidphotoconductor.

a coated thereon a photoconductive composition compris- (a) about 10 to60% by weight based on said photoconductive composition of ethylp-diphenylaminocinnamate as a photoconductor,

(b) about 0.005 to 5.0% by weight based on said photoconductivecomposition of a pyrylium salt as a sensitizer, and

(c) poly(vinyl meta-bromobenzoate-co-vinyl acetate) as a binder for saidphotoconductor.

17. In an electrophotographic process wherein an electrostatic chargepattern is formed on an electrophotographic element, the improvementcharacterized in that the charge pattern is formed on theelectrophotographic element of claim 4.

References Cited UNITED STATES PATENTS 2,766,233 10/ 1956 Kartinos260-240 3,180,730 4/1965 Klupfel 961 3,221,041 11/1965 Roland 260-4653,265,496 8/1966 FOX 96-1 3,387,973 6/1968 FOX et al. 96-1.5

GEORGE F. LESMES, Primary Examiner J. C. COOPER, III, Assistant ExaminerUS. Cl. X.R.

